An asteroid is headed for Earth... and some fun space rock facts

Asteroids hold many secrets about the origin of life on Earth (Image: Getty)

In just over two weeks, the light metal capsule will descend from space into the Utah desert.

It’s a human skill, but it will be filled with alien matter – samples picked up from the dark and dusty atmosphere of a near-Earth asteroid.

Called Bennu, it is now about 75 million kilometers away, and will shed new light on the formation of the solar system 4.5 billion years ago.

However, we already know a lot about the early years of our neighborhood thanks to another type of cosmic object – meteorites.

Meteorites are basically space rocks, ranging in size from dust particles to large asteroids, that survive the fire through the Earth’s atmosphere.

And they are amazing.

Nuclear scientist and meteorite fan Tim Gregory shares nine interesting facts about these amazing space travelers.

Nuclear physicist Tim Gregory explains why meteorites are so amazing (Image: Tim Gregory)

They are basically time capsules

When the solar system was formed, it was a huge cloud of gas and dust – a nebula – like all these beautiful photos Hubble and the James Webb Space Telescope are sending back.

We were one of those great interstellar clouds. Then, about four and a half billion years ago, a small lump of that cloud began to stick to itself.

The Carina Nebula, the stellar nursery where new stars are born, captured by the James Webb Space Telescope (Image: Nasa)

As the center of the cloud grew thicker and denser, its gravitational force grew and grew, and so the collapse surrounded the runner. Most of that, about 99.9% of it, makes up the Sun. The rest formed planets and everything else – moons, comets, and asteroids.

But that’s just the general picture – there are a lot of nitty gritty details on how you get from the nebula to the solar system. There are two ways we can investigate: telescopes, and meteorites.

Meteorites are debris left over from the time when the planet was formed. They are small pieces of asteroids. They pre-formed the planets, forming the oldest rocks in the solar system.

Studying meteorites in detail helps explain the origins of the solar system (Image: Tim Gregory)

And in physics, what is true of a teacup is true of an asteroid. Small objects cool faster than large objects. Asteroids, therefore, lost their heat quickly after they formed in the early solar system. Since then, they have remained unchanged.

Meteorites are geological time capsules, and we can start them by using the ‘radioactive clocks’ that are naturally present in all rocks. Radioactive elements – such as uranium – decay into new elements at a rate determined by their lifetime. By measuring how much radioactive decay has occurred in a meteorite, you can estimate its age. Using this method, we determined the age of the solar system: 4.6 a billion years old.

Sometimes the Moon throws stones at us

Almost all meteorites come from asteroids, but it is very difficult to tell which meteorite comes from which asteroid.

However, sometimes we know exactly where they come from, as in the case of lunar meteorites. As the name suggests, they come from the Moon.

Anyone can see craters on the Moon made by asteroid strikes and meteorites (Image: Reuters)

And the reason we know they came from the Moon is because we can compare them like-for-like to the rocks that the Apollo astronauts brought back. We can compare geology – and they seem to match perfectly.

But how did they get here? Because the Moon doesn’t have an atmosphere, it’s a floating lake for asteroids and meteorites – as you can see on Earth through the many craters that cover its surface. When hit, pieces of the Moon fly, and if the angle is right, they crash to the ground.

Some are more unusual

The second type of meteorite that we have a very good idea of where they come from areMartian meteorites. Oh yeah, meteorites from Mars.

Now, while we don’t have Mars samples to compare to Earth (yet), there are two major lines of evidence to tell us where it came from.

First, their age. They are much, much younger than all other meteorites, sometimes billions of years younger. They must have come from a celestial body that was geologically active recently – and there aren’t many of those around the sun.

Nasa’s Perseverance rover captured this image of a possible meteor on Mars – some impacts could break up pieces of the planet that fall to Earth (Image: Nasa/JPL-Caltech/LANL/CNES/IRAP)

Second, although we haven’t returned any Mars samples from the mission, we have sent our robotic ambassadors to the surface of Mars: raiders and raiders. They tested the chemistry of the atmosphere there, and it matched perfectly with the chemistry of the gas in these meteorites.

I will never forget the first time I held it. I always thought it would be a future astronaut who touched the surface of Mars first, but we did it decades ago, which is cool.

The ingredients of life?

There is a rare type of meteorite called carbonaceous chondrites. Clear chondrites are the most common type of meteorite, the oldest type.

But carbonaceous chondrites are the most important type of meteorite – and my favorite.

Carbonaceous chondrites have been found to contain the building blocks of life (Image: Tim Gregory)

As the name suggests, they are often rich in carbon, and the type of carbon we get from them is varied and complex.

But the most unexpected type of chemistry we find in them is amino acids.

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And amino acids are the building blocks of life on Earth.

Now that doesn’t mean this is proof of extraterrestrial life, although people suspected it when it was first discovered. But it means two things.

First, meteorites could have brought the building blocks of life to Earth from space.

And secondly, the building blocks of life are abundant in the solar system. In my mind, this greatly increases the likelihood that there is life elsewhere in our solar system.

They smell

Nine years ago, I was an intern at NASA’s Johnson Space Center, and my summer project was to study one of these carbonaceous chondrites, which were discovered in Antarctica in 1994.

I read stories about the smell of these meteorites, so as soon as I opened it, I took a deep breath – and it really smelled! It smelled kind of organic-y, actually like a wet towel, very nice smell.

Meteorites can be the world’s waiter

Is anyone drinking?

There is a strong theory that Earth’s water was delivered by comets, but the isotopic composition of the ice found in them does not match what we have in our rivers, oceans, and taps.

However, carbonaceous chondrites are full of water, and their composition is very similar to that of ground water.

Tim’s carbonaceous chondrite – containing a surprising amount of water (Photo: Tim Gregory)

Some of these meteorites are maybe 10 or 20 percent water. But not water as we are used to it – you can’t wrap it like flannel. It’s bound to the crystal structure inside the meteorite, but there’s still enough of it that they can bring water to Earth, which is, of course, essential for life.

We have a lot to thank carbonaceous chondrites for!

Carver of royal head right

Now, here’s something interesting. When they broke open Tutankhamun’s tomb just 100 years ago, wrapped next to him in his linen shroud, there was a long sword enclosed in this golden case.

But the iron blade was made of iron, which was a bit of a head scratcher for the archaeologists who found it – because it was before the Iron Age.

And even for a stranger, the chemistry of the sword matches perfectly with the chemistry of iron meteorites.

Tutankhamun was buried with a sword from this country (Image: Getty)

This leads to the strange but inevitable conclusion that Tutankhamun’s sword was made from an iron meteorite.

We will never know for sure that the person who made the sword knew that the iron came from outer space. But what we do know is that, around the same time as Tutankhamun, a new hieroglyph was similarly used – and its literal translation is ‘iron from the sky’.

There are literally tons of meteorites headed our way

What is the chance of being hit by a rocket from the sky? Basically zero.

However, about 40,000 tons of extraterrestrial rocks fall to Earth every year. Fortunately, the world is so big, that 40,000 tons spread out very little.

Of course, sometimes large ones hit the Earth and can cause damage, like the Chelyabinsk meteorite over Russia in 2013.

And sometimes they hit hard, maybe 66 million years ago in the Yucatán peninsula, which completely wiped out the dinosaurs.

Another big one may be on the way

Extinction-level asteroids are very rare, but there is a chance they will hit Earth in the second half of the next century. That sounds a long time in the future, but it’s not that far, only about 150 years – a couple of generations.

Sinner? Asteroid Bennu, which NASA recently visited to collect samples. There is about a 1 in 3,000 chance of it reaching Earth.

That would be like detonating several thermonuclear devices at once. All in one place. It will be very bad.

But what is almost poetic is that Bennu is a carbonaceous asteroid.

So carbonaceous asteroids and meteorites probably brought the building blocks of life to Earth, and one can absorb a little of it.

Tim Gregory is a full-time nuclear scientist at the heart of Britain’s nuclear industry at Sellafield. He will be speaking at New Scientist Live at ExCeL London on Saturday, October 7. His first book, Meteorite: How Stones from Outer Space Made our World, is available to buy now.

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